Partial chemical/structural elucidation of anti-mutagenic compounds from corn.

In this study, corn fractions obtained from an isolation process of anti-mutagenic factors in our previous research work (Burgos-Hernández et al., 2001), were subjected to several analyses for chemical/structural elucidation. The anti-mutagenic activity of these fractions was tested against aflatoxin B(1) (AFB(1)) and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), a mutagen that does not require bioactivation. Two concentrations of this agent in the corn fractions were tested for anti-mutagenicity in the Salmonella/microsomal mutagenicity assay, using tester strain TA100 with no metabolic activation. Corn fractions tested showed evidence of anti-mutagenic activity by producing a dose-response type of relationship between a constant amount of MNNG and several concentrations of tested corn fraction. Five different varieties of yellow corn were tested in order to determine if the anti-mutagenic factors were intrinsic to corn. Variety of the corn did not show an effect on the reduction of the mutagenic potential of AFB(1) suggesting that anti-mutagenic compounds are intrinsic to corn. Four corn fractions, previously obtained after the isolation process were analyzed by MALDI-MS and GC-MS. MALDI-MS showed the presence of two groups of molecules or molecular fragments. The molecular mass of one group ranged from 250 to 370 m/z, the other ranged from 540 to 640 m/z. GC-MS identified linoleic acid as one of the compounds responsible for the anti-mutagenic activity present in corn.

Anti-mutagenic compounds from corn.

In previous studies with aflatoxin-contaminated corn an uncharacteristic response for AFB1 in the Salmonella/microsomal mutagenicity assay (Ames test) was observed and the presence of anti-aflatoxin factors in the corn was suggested. In the current study, corn was extracted and fractionated using thin layer chromatography (TLC) using different developing solvent systems and the Ames test was used to monitor for anti-mutagenic activity in the corn fractions. Both Salmonella tester strains TA98 and TA100 with metabolic activation (S9) were used. Several corn fractions, at different stages in the isolation and purification process, showed anti-mutagenic dose-responses when exposed to pure AFB1. Corti extracts were non-toxic to the tester strains and TLC fractions that showed the best anti-mutagenic dose-responses were selected for further partial characterization analyses.

Performance of three pneumatic probe samplers and four analytical methods used to estimate aflatoxins in bulk cottonseed.

The requirement by the U.S. Food and Drug Administration that agricultural products susceptible to aflatoxin contamination contain aflatoxin at levels < or =20 parts per billion for consumer-ready products has led to the establishment of inspection programs by various industries. In Arizona, cottonseed samples from 100 ton piles are collected by an accumulation of 3 or more probings with a pneumatic probe. When sampling compacted cottonseed piles, the large official pneumatic probe (7.6 x 127 cm) decreases in efficiency. Two smaller probes (1.9 x 127 cm and 1.9 x 254 cm ) were therefore developed and tested for their suitability for sampling cottonseed piles. Three rapid analytical methods (one thin-layer chromatographic and 2 immunochemical) were tested for suitability as on-site assay systems. An analysis of variance of the analytical test results showed no differences between the various probes tested. Of the rapid methods, however, only the AflaTest-P immunoaffinity column gave results similar to those of the official AOAC thin-layer chromatography method. In terms of safety, however, all methods prevent material contaminated above regulatory limits from reaching the consumer.